Sand seal for tunnel kilns



Patented Feb. 21, 1933 more!) STATES PATENT orrice EDWIN B. FORSE ANDCHARLES F. GEIGER,

OF METUCHEN, NEW JERSEY, ASSTGNORS TO THE CARBOEUNDUM COMPANY, OFNIAGARA FALLS, NEV] YORK, A CORPORA- TION OF PENNSYLVANIA SAND SEAL FOR.TUNNEL KILNS Application filed October 24, 1930, Serial No.

This invention relates to a method of sealing in tunnel kilns and othercontinuous or periodic car type furnaces. This application is acontinuation in part of our prior application U. S. Serial No. 276,222,filed May 8,

In the ordinary use of sand seals in tunnel kilns a number ofdifiiculties have developed principally from the overheating of theplatform of the car truck and the consequent overheating of the gearbeneath the car platform. The ordinary sand seal includes metal platesor aprons which depend from the car platform into sand troughs whichextend along each side of the tunnel wall, the sand troughs beinglocated a little above the car axle. The sand trough is considerablybelow the top of the car platform. In this type of seal it is found thatfor any extended run of a continuous tunnel kiln such great clearancesmust be provided between the car platform and the kiln wall thatcombustion gases have ready access to the sides of the platform and tothe aprons which depend therefrom into the sand. Under these conditionsthe platform of the car and the running gear underneath the platformbecome unduly heated, causing rapid corrosion and resulting highmaintenance costs for sand seal plates, wheels, bearings, etc. Highleakage through the overheated sand seal or through corroded metal partstends to cause poor atmospheric control in the kiln chamber.

Attempts have been made to overcome these diniculties by giving thepassage between the car platform and the tunnel wall a Zigzag form (in avertical plane) to increase the resistance to the movement of highlyheated gases from the region above the platform toward the sand trough.It is found necessary, however, to employ large clearances between thecars and the wall because in operation the expansion tendencies whichare cumulative cause the cars to be- 490,939, and in Great Britain July3, 1928.

come wider and the kiln structure to be come narrower internally for thereason that the kllIl walls are prevented from moving outwardly by thebracing required to im- To overcome the difficulties referred to abovethe applicants have taken advantage of the fact that in kilns andfurnaces of the type under consideration the vertical expansion is muchless than the transverse expansion. The applicants have also madeprovision for additional sealing means at the top of the car platform.

The improved sealing arrangements are illustrated by the accompanyingdrawing in which:

Figure 1 is a vertical section of the lower portion of a tunnel kilntaken in a plane at right angles to its length; and

Figure 2 shows a modification of the form shown in Figure 1, and showsdetails of its particular sealing means on an enlarged scale.

Referring to the drawing in more detail, a car is mounted to run onrails 3- and is provided with an apron 4 extending into a sand trough 5.From the sides of the kiln wall extend ledges 6 of refractory material.The ledges 6 present rectangular edges 7 which are so situated withrespect to corresponding recesses 8 of rectangular section in the blocks9 carried by the cars that sand may be retained in considerablequantities between the ledges 6 and the corners 8 of the blocks 9. Thesand so retained forms seals adjacent to the upper surface of the block9 which are useful in greatly reducing the penetration of furnace gasesinto the region between the platform and the'tunnel wall and extendingfrom the sand seal 5 to the ledge 6. In order to obtaln the manmumbenefit from this type of seal it is desirable that the construction besuch that as each car passes further and further into the furnace theclearance between the ledge 6 adjacent to the edge 7 and the block 9becomes decreasingly less. As long as there is sufficient sand in thisupper seal continuous contact is maintained between the ledge block 6and the sand in the complementary recess to prevent the passage of gasesthrough the intervening sand. Sand which is scraped from the shelf 11falls down to lower sand seals. Instead of ordinary sand (SiO finelycrushed material such as silicon carbide grain or powdered materialcomposed of fused alumina, periclase, etc. may be employed as thesealing medium.

In the modification shown in Figure 2 two sand seals are shown adjacentthe upper surface of the car platform. One of these seals is formed inthe space between a rectangular recess in the refractory block 15(mounted on the car) and the stationary ledge 16 which projects from thefurnace wall. Below the sand seal just described is a recess 17 in thefurnace wall. Sand which is scraped from the uppermost sand seal fallson a stationary ledge 18 and a seal is thus built up between the corner19 of the a block 15 and the rectangular recess bounded by the ledge 18and the vertical portion of the furnace wall denoted 20. The projectionof the block 15 into the recess 17 affords a radiation shield from thehotter regions above the block 15 even when the amount of sand in theuppermost seal is small.

We claim:

1. In a tunnel kiln a car track, a refractory platform mounted to run onsaid track between the side walls of the tunnel, and means for reducingthe transfer of heat from the chamber above the platform to the runninggear underneath, said means comprising a projection from a side wall ofthe tunnel into a sand pocket included between the top of the platformand a projection extending laterally from the platform at a shortdistance below the top and into a recess below said wall projection toform an overflow sand seal fed from said firstmentioned seal, theprojection from the side wall being sloped downward toward the track toprovide a gradually diminishing clearance in the first-mentioned sandseal,

and a third seal formed by a thin plate extending down from the platforminto a sand trough arranged to catch sand from said second sand seal.

2. In a tunnel kiln, a car having a refractory platform for carryingware, side walls of said kiln adjacent said platform and interfittingtherewith to form an overlapping ledge, a seal of loose granularrefractory material on said ledge in contact with the tures.

EDWIN B. FOR-SE. CHARLES F. GEIGER.

